Dynamic Stability of FPSO-Shuttle Systems: An Analytical Procedure and Practical Results

2002 ◽  
Author(s):  
Ge´rson B. Matter ◽  
Joel S. Sales ◽  
Sergio H. Sphaier
Keyword(s):  
Dynamic Stability ◽  
Deep Water ◽  
Dynamic Systems ◽  
Time Domain ◽  
Equilibrium Position ◽  
Analytical Procedure ◽  
Time Domain Analysis ◽  
The Stability ◽  
The Time Domain ◽  
Floating Systems

The paper deals with the dynamics of floating systems (FPSO units) moored in deep water in the presence of currents. The offloading operation is carried out in a tandem arrangement from the FPSO to a Shuttle ship of lesser capacity. According to the classical theory of dynamic systems, a study of the behavior of floating units is performed by determining the equilibrium position and then analyzing the stability around this position. The time domain analysis is also used to compare the results. This procedure is extended to the case of systems in a spread mooring configuration and with turret.

Nonlinear modeling, time-domain analysis and simulation of non-Foster elements

2016 ◽  
Vol 9 (4) ◽  
pp. 747-755
Author(s):  
Hamed Khoshniyat ◽  
Abdolali Abdipour ◽  
Gholamreza Moradi
Keyword(s):  
Time Domain ◽  
Linear Time ◽  
Nonlinear Modeling ◽  
Current Source ◽  
Time Domain Analysis ◽  
Circuit Performance ◽  
Modeling Analysis ◽  
The Stability ◽  
The Time Domain ◽  
Good Agreement

In this paper, the structure of a common field-effect transistor (FET)-based negative impedance converter (NIC) that behaves as a negative capacitor is presented. The nonlinear modeling, analysis, and simulation of this non-Foster structure are presented in the time domain and the transient response of the circuit can be used to study the stability of the circuit. For the analysis of the circuit performance, the linear time-dependent modeling approach is used. This method is based on determination of the circuit parameters at each step according to parameters of the previous steps, bias voltages, and the input signal. Results of the proposed method for analysis of non-Foster circuit are compared with those of nonlinear analysis using commercial software, which shows a good agreement together and the proposed method is validated. Based on the analysis, the nonlinear capacitance of non-Foster circuit is extracted and based on the simple second order model of current source of FET, the analytic model of negative capacitor is extracted and improved by curve fitting. The proposed model results have a good agreement with simulation results of NIC's circuit.

A Conjoint Analysis of the Stability and Time-Domain Analysis on Floating Platform During Mooring Line Breaking

2019 ◽  
Author(s):  
Jiaguo Feng ◽  
Yi Yu ◽  
Yan Qu ◽  
Wenhui Xie ◽  
Min Wu ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Time Domain ◽  
Stability Problem ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Mooring Line ◽  
Floating Platform ◽  
The Stability ◽  
The Time Domain ◽  
Floating Platforms

Abstract The stability of platform is important to ensure the platforms are safe, especially during the mooring line breaking process in typhoon condition. The paper presents a stability analysis method for floating platforms of the mooring line breaking process based on the time-domain analysis. The time-domain simulation during the mooring line breaking is provided. The time of the mooring line break, the max tilt angle of platform and the amended equivalent overturning moment are calculated for the stability analysis. The results show that the platform would have a serious tilt when the mooring line breaks, this increases the overturning moments and may cause the platform not meets the stability requirements during this process. It is necessary to pay attention to the stability problem during the mooring line breaking process in typhoon condition. And properly locating the down-flooding points is recommended to avoide the stability problem.

Experimental Study on the Performance of Constrained Damped Rail Vibration Reduction

2011 ◽  
Vol 42 (10) ◽  
pp. 9-14
Author(s):  
L.Y. Liu ◽  
J.Y. Li ◽  
X.J. Yin
Keyword(s):  
Experimental Study ◽  
Time Domain ◽  
Vibration Amplitude ◽  
Impact Load ◽  
Vibration Reduction ◽  
Time Domain Analysis ◽  
Experimental Basis ◽  
Vibration Acceleration ◽  
The Time Domain ◽  
Vibration Performance

To study the vibration reduction performance of damped rail, we take the standard rail and labyrinth constrained damped rail as the study target. By testing the vibration performance of both standard rail and labyrinth constrained damped rail in an anechoic room, we use the time-domain analysis to study the vibration changes with time passing. The results showed that: the labyrinth constrained damped rail vibration can effectively reduce the vibration amplitude and duration. Under the radial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 5% −19%, time of vibration and attenuation greater than 94%; under the axial impact load, compared to the standard rail, vibration acceleration attenuation of the labyrinth constrained damped rail is 9% −21%, time of vibration and attenuation greater than 92%. The results have provided an experimental basis for the design of new constrained damped rail.

Numerical Simulation on Mooring Performance of LNG-FPSO System in Realistic Seas

2005 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Time Domain ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Time Domain Analysis ◽  
Analysis Tool ◽  
Motion Response ◽  
Non Linear ◽  
Floating System ◽  
Exciting Forces ◽  
The Time Domain

The LNG-FPSO concept is receiving much attention in recent years, due to its active usage to exploit oil and gas resources. The FPSO offloads LNG to an LNG carrier that is located close to the FPSO, and during this transfer process two large vessels are in close proximity to each other for daylong periods of time. Due to the presence of neighboring vessel, the motion response of both the vessels will be affected significantly. Hydrodynamic interactions related to wave effects may result in unfavorable responses or the risk of collisions in a multi-body floating system. Not only the motion behavior but also the second order drift forces are influenced by the neighboring structures due to interactions of the waves among the structures. A study is made on the time domain analysis to assess the behavior and the operational capability of the FPSO system moored in the sea having an LNG carrier alongside under environmental conditions such as waves, wind and currents. This paper presents an analysis tool to predict the dynamic motion response and non-linear connecting and mooring forces on a parallel-connected LNG-FPSO system due to non-linear exciting forces of wave, wind and current. Simulation for the mooring performance is also investigated. The three-dimensional source-sink technique has been applied to obtain the radiation forces and the transfer function of wave exciting forces on floating multi-bodies. The hydrodynamic interaction effect between the FPSO and the LNG carrier is included to calculate the hydrodynamic forces. For the simulation of a random sea and also for the generation of time depended wind velocity, a fully probabilistic simulation technique has been applied. Wind and current loads are estimated according to OCIMF. The effects of variations in wave, wind and current loads and direction on the slowly varying oscillations of the LNG and FPSO are also investigated in this paper. Finally, some conclusions are drawn based on the numerical results obtained from the present time domain simulations.

scholarly journals Time-domain analysis of distortion-product otoacoustic emissions using a hydrodynamic cochlea model

2017 ◽  
Vol 3 (2) ◽  
pp. 453-456
Author(s):  
Dennis Zelle ◽  
Ernst Dalhoff ◽  
Anthony W. Gummer
Keyword(s):  
Time Domain ◽  
Otoacoustic Emissions ◽  
Short Pulse ◽  
Human Subjects ◽  
Time Domain Analysis ◽  
Distortion Product Otoacoustic Emissions ◽  
Sound Waves ◽  
Cochlear Function ◽  
Distortion Product ◽  
The Time Domain

AbstractAs a by-product of nonlinear amplification in the cochlea, the inner ear emits sound waves in response to two tones with different frequencies. These sound waves are measurable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). DPOAEs putatively consist of two components emerging at different locations in the cochlea. Wave interference between the two components limits the accuracy of DPOAEs as a noninvasive measure of cochlear function. Using short stimulus pulses instead of continuous stimuli, the two DPOAE components can be separated in the time domain due to their different latencies. The present work utilizes a nonlinear hydrodynamic cochlea model to simulate short-pulse DPOAEs in the time domain. When adding irregularities to the mechanical parameters of the model, the simulated DPOAE signals show two distinguishable components and long-lasting beat tones, similar to band-pass filtered experimental data from normal-hearing human subjects. The model results suggest that the beat tones can occur solely due to interference of the coherent-reflection component with the fading nonlinear-distortion component.

scholarly journals Two optical emission components with different variability in V404 Cygni

2016 ◽  
Vol 12 (S324) ◽  
pp. 43-44
Author(s):  
Yutaro Tachibana ◽  
Taketoshi Yoshii ◽  
Nobuyuki Kawai
Keyword(s):  
Spectral Index ◽  
Power Law ◽  
Time Domain ◽  
Optical Emission ◽  
Time Domain Analysis ◽  
Blackbody Radiation ◽  
Light Curves ◽  
Variable Component ◽  
Single Temperature ◽  
The Time Domain

AbstractV404 Cygni went into an outburst again on June 15, 2015 after 26 years of quietness. Soon after the notifications, we started intense optical observation campaign of this source. The spectral index between RC and IC-band was stable over the outburst, whereas that between g′ and RC-band varied violently. With the time domain analysis of the multi-color optical light curves, we successfully decomposed optical variations into three components: highly-variable component (HVC), little-variable component (LVC). The loci of the LVC in the color-color diagram is consistent with that of a single temperature blackbody radiation or a multi-color blackbody radiation from a standard accretion disk, while those of the HVC trace that of power-law spectra.

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